Selector switch for regulating transformers



Dec. 23, 1969 A, BLElBTREU ET AL 3,485,965

SELECTOR SWITCH FOR REGULATING TRANSFORMERS Filed Oct. 2, 1967 United States Patent M ,2 Int. Cl. H01h 19/58, 21/78, 3/00 U.S. Cl. 20011 4 Claims ABSTRACT OF THE DISCLOSURE A selector switch for tap-changing regulating transformers including a plurality of fixed contacts intended to be conductively connected to taps of a tapped transformer winding. The aforementioned fixed contacts are arranged 1n a circular pattern. Some of the plurality of fixed contacts have an unequal circular pitch. A pivotable contact arm is adapted to engage each of the aforementioned plurality contacts. This contact arm is operated by a geneva gear having a special shape adapting the geneva gear to compensate for the unequal pitch of the fixed contacts. In other words, the contact arm is being moved in steps involving different angles corresponding to the arrangement of the fixed contacts.

BACKGROUND OF THE INVENTION The basic elements of most selector switches for tapped regulating transformers are a plurality of fixed contacts arranged in a circular pattern and intended to be conductively connected to taps of a tapped transformer winding, and a contact arm pivotable about an axis situated in the center of said circular pattern, said contact arm having a movable contact adjacent the radially outer enel thereof for engaging each of said plurality of fixed contacts. All the fixed contacts may have an equal circular pitch or the circular pitch of some of the fixed contacts may differ from the circular pitch of others of the fixed contacts. If the circular pitch or the spacing of the fixed contacts is determined by their difference in potential, as it should be for soundness of design, an unequal circular pitch of the fixed contacts results.

This fact leads to complications which have not been successfully resolved to date.

Attempted solutions of the problem are geneva gear drives for the contact arm including a pair of geneva gears both operatively related to the contact arm for operating the latter. These geneva gear drives are, however, very complex for reasons which will be apparent from what follows.

It is common practice to arrange the fixed contacts of selector switches in two coaxial circular patterns which are arranged in a pair of parallel, spaced, planes, i.e. horizontal planes. The fixed contacts arranged in one plane are conductively connected to the even numbered taps of a tapped transformer winding, and the fixed contacts arranged in the other plane are conductively connected to the odd numbered taps of a tapped transformer winding. The fixed contacts in each plane may be scanned by a rotatable contact arm. If the circular pitch of all the fixed contacts in both planes is not equal, and this is compensated along prior art lines by the provision of a double geneva gear drive per pivotable contact arm, the provision of four geneva gears becomes necessary, and this is not compatible with normal space requirements. In any such arrangement involving two double geneva gear drives,

or four geneva gears, it becomes generally necessary tov 3,485,965 Patented Dec. 23, 1969 provide two rotatable crank shafts, each for operating one of the double geneva gear drives. This further increase in bulk is very undesirable.

The present invention is an effective solution to the problem of minimizing cost and space requirements for the drive of selector switches having fixed contacts whose circular pitch is not equal. To be more specific, the present invention solves the problem of providing selector switches for tapped regulating transformers whose fixed contacts have a circular pitch which is not equal with geneva gear drives which do not increase the cost and space requirements for the drives of the selector switches above and beyond those applicable to selector switches for tapped regulating transformers wherein all contacts have the same circular pitch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top-plan view of a selector switch embodying this invention, including two sets of fixed contacts which are arranged in spaced horizontal planes, the drive of the contact arms, or contact bridges, being deleted in FIG. 1;

FIG. 2 is a vertical section of the drive for the selector switch of FIG. 1 taken along 11-11 of FIG. 3; and

FIG. 3 is a top-plan view of the drive shown in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION In the drawings reference character Tr has been applied to indicate the tapped portion of a transformer winding. The winding Tr has fourteen taps to which numerals 1, 2, 3, 4 12, 13, 14 have been applied. The selector switch includes a first plurality of fixed contacts 1, 3, 5 9', 11', 13 conductively connected to the odd numbered taps of transformer winding Tr. These contacts are arranged in a horizontal plane and in a circular pattern. The selector switch further comprises a second plurality of fixed contacts 2', 4', 6' 10', 12', 14 conductively connected to the even numbered taps 2, 4, 6 10, 12, 14 of transformer winding Tr. These contacts are arranged in a circular pattern coaxial with fixed contacts 1, 3', 5' 9', 11', 13' and arranged in a plane parallel to, and spaced from, the plane in which contacts 1, 3, 5' 9', 11, 13' are arranged. The odd numbered contacts 1', 3', 5' 9', 11', 13 are arranged in a plane at a lower level than the plane in which the even numbered contacts 2', 4', 6 10', 12, 14 are arranged. The circular pitch or angular spacing of contacts 1' and 3'; 2 and 4; 3' and 5, etc. is different from the circular pitch, or angular spacing, of contacts 12' and 14, 13 and 1', and 1-4' and 2. The last mentioned circular pitch, or angular spacing, exceeds the first mentioned circular pitch, or angular spacing, because of the larger difference in voltage between the fixed contacts 12', 14'; 13', 1' and 14', 2'.

The fixed contacts 1, 2', 3', 4', 5' 10', 11', 12, 13', 14' are mounted on a squirrel-cage like structure formed by vertical insulating rods which are arranged in a cylindrical surface. Such an arrangement of the fixed contacts of a selector switch for tapped insulating transformers has been disclosed in considerable detail in U.S. Patent 3,250,864 to A. Bleibtreu et al., May 10, 1966 for REGU- LATING TRANSFORMERS HAVING A LARGE NUMBER OF TAPS and reference may be had to this patent in regard to details of the selector switch having no immediate bearing on this invention.

Reference numerals 21, 22 have been applied to indicate a pair of contact arms, or contact bridges, having contacts adjacent the radially outer ends thereof. Contact arms, or contact bridges 21, 22 are pivotable about an axis situated in the center of the circular pattern formed by contacts 1', 2', 3', 4' 10', 11', 12', 13', 14'. This axis is at right angles to the two parallel planes defined by fixed contacts 1', 3', 5 9, 11, 13 and by fixed contacts 2, 4, 6' 12', 14. Contact arm, or contact bridge, 21 is adapted to cooperatively engage the odd numbered fixed contacts 1', 3', 5' and contact arm, or contact bridge, 22 is adapted to cooperatively engage the even numbered contacts 2, 4, 6 As shown in FIG. 1 contact bridge, or contact arm, 21 is in engagement with fixed contact 1', and contact bridge, or contact arm, 22 is in engagement with fixed contact 14'.

Reference numeral 25 has been applied to indicate an insulating column arranged in the center of the circular patterns formed by contacts 1', 2', 3', 4' or in coaxial relation with the circular patterns formed by fixed contacts 1', 2', 3', 4' The lower end of insulating column 25 supports a pair of slip rings 23, 24, of which the former is slidably engaged by the radially inner side of contact arm, or contact bridge, 21 and the latteris slidably engaged by the radially inner side of arm, or contact bridge, 22. Thus contact arm, or contact bridge, 21 establishes a conductive connection between the odd numbered fixed contacts 1', 3, 5 and slip ring 23, and contact arm, or contact bridge, 22 establishes conductive connections between the even numbered fixed contacts 2', 4', 6 and slip ring 24. The lower end of insulating rod 27 is secured to contact arm, or contact bridge, 21 and extends parallel to the axis of insulating column 25, and its upper end is affixed to a Geneva gear 31, operating contact arm, or contact bridge, 21 by the intermediary of rod 27. In a like fashion the lower end of insulating rod 28 is secured to contact arm, or contact bridge, 22 and its upper end is afiixed to a Geneva gear 32, operating contact arm, or contact bridge, 22 by the intermediary of rod 28. In other words, rods 27, 28 are torque-transmitting means for transmitting torques from Geneva gears 31 and 32 to contact bridge 21 and 22, respectively. Geneva gears 31 and 32 are operated intermittently in discrete steps corresponding to the circular pitch or spacing of fixed contacts 1', 2', 3', 4 The Geneva gears 31 and 32 are, in turn, operated by a crank mechanism including an arm 33 arranged in a plane parallel to the planes in which contacts 1', 2', 3", 4' are arranged and having two pin means, or cam means, 35 and 36 angularly displaced 180 degrees. Arm 33 is mounted on shaft 33a and driven by shaft 33a. Pin means35 engage Geneva gear 31, and move the latter in discrete steps, and pin means 36 engage gear 32, and move the latter in discrete steps. Geneva gears 31 and 32 are mounted on a hollow shaft, or tubular member, 34 which is supported on and by the upper end of the insulating column 25.

As clearly shown in FIG. 3 each of the Geneva gears 31, 32 has a plurality of recesses having openings into which pins 35 and 36, respectively, may enter, and thus transmit a torque from crank arm 33 to Geneva gears 31 and 32, and contact bridges 21 and 22. Each Geneva gear is provided with funnel-shaped recesses 37 and 37, respectively. These recesses have a relatively wide radially outer open entrance portion and a relatively narrow closed radially inner portion. The open entrance portion is flaring outwardly, and the radially inner portion is bounded laterally by a pair of parallel radial walls. In addition thereto Geneva gears 31, 32 are provided with recesses 38 and 38, Geneva gear 32 being provided with two recesses 38'. Recesses 38 and 38' have the same width at their radially outer open entrance and at their radially inner closed end. The width of recesses or slots 38, 38 is constant throughout the entire length thereof. The geometry of recesses 37, 37, 38, 38' is determined by the circular pitch, or angular spacing, of fixed contacts 1', 2', 3', 4'

which, in turn, is determined by the difference in potential between the aforementioned fixed contacts. The recesses 37, 37 reflect an equal circular pitch, or angular spacing, between fixed contacts, and the recesses 38, 38

.4 reflect, or are necessitated by, an increased circular pitch, or angular spacing, between fixed contacts. Assuming that the arrangement of the fixed contacts would require one of the contact bridges to perform two relatively larger steps, in addition to a number of equal steps, such condition can readily be met by providing one Geneva gear, i.e. Geneva gear 32, with a pair of recesses 38' of constant width rather than one single such recess. This has been shown in FIG. 3.

FIG. 3 clearly illustrates the effect of recesses 37, 37' and 38, 38' on the law of motion to which contact bridges 21, 22 are subjected. As shown in FIG. 3, pin 35 is about to engage the recess 38 in Geneva gear 31, and this results in a pivotal motion of Geneva gear 31 about a predetermined relatively large angle. The fact that this angle is relatively large is caused by an early driving engagement between pin 35 and Geneva gear 31, and a late disengagement of pin 35 from gear 31. In other words, pin 35 begins to drive Geneva gear 31 when the trajectory of pin 35 intersects the periphery of Geneva gear 35 at the entrance of recess 38, and pin 35 stops driving Geneva gear 31 when pin 35 re-intersects the periphery of Geneva gear 31. The same applies in regard to pin 36 and the two recesses 38 in Geneva gear 32. When pin 35 enters one of recesses 37 in Geneva gear 31, pin 35 may travel from the periphery of the gear 31 to a point relatively close to its center before a positive engagement, or driving engagement, is established between pin 35 and Geneva gear 31. The same applies in regard to pin 36 and recesses 37'. As a result, engagement of recesses 37 and 37' by pins 35 and 36 causes but relatively limited angular movements of Geneva gears 31 and 32. The angle of this movement can be determined precisely by imparting appropriate shapes to the axially outer open ends of recesses 37, 37.

Pin 36 on arm 33 engages Geneva gear 32 following a pivotal movement of arm 33 of deg. This movement is counterclockwise, as indicated by an arrow in FIG. 3, and the motion of 180 degrees is counted from the position of parts shown in FIG. 3.

Thus Geneva gears 31 and 32 are being driven alternately by crank mechanisms 33, 35, 36, and consequently contact arms 27 and 28 are being operated in alternate steps alternating between even fixed contacts and odd fixed contacts. The movement of contact arms 21, 22 may either be clockwise, or counterclockwise, depending upon the sense of rotation of crank-mechanism 33, 35, 36.

It will be noted that there are three even numbered fixed contact, i.e. contacts 12', 14, 2' having a larger circular pitch, or angular spacing, than the other even numbered fixed contacts. There are two odd numbered fixed contacts, i.e. contacts 13', 1 having a larger circular pitch, or angular spacing, than the other odd numbered fixed contacts: Consequently the geneva gear 32 operating contact arm 22 engaging the even numbered fixed contacts 2', 4', 6' is provided with two recesses 38 having relatively narrow open entrance portions, while geneva gear 31 operating contact arm 21 engaging odd numbered fixed contacts 1, 3', 5 is provided with one recess 38 having a relatively narrow entrance portion. It will further lbe noted that the angular spacing of the recesses 37, 37 of geneva gears 31, 32 having widely radially outwardly flaring entrance portions is relatively small, while the angular spacing of the recesses 38, 38' having relatively narrow entrance portions from recesses 37 and 37', respectively, of geneva gears 31 and 32, respectively is relatively large.

It will be apparent from the above that compliance with the laws of motion of geneva gears 31, 32 required by the unequal circular pitch of fixed contacts 1', 3', 5' 9', 11', 13 and fixed contacts 2, 4, 6' 10, 12', 14' is achieved on account of the fact that the width of the radially inner closed ends of recesses 37 and 38, and 37' and 38', respectively, is equal, while the width of the radially outer open ends of recesses 37 and 38,

and 37' and 38', respectively, is unequal. In other words, the width of the radially outer open ends of recesses 37 exceeds that of recesses 38, and the width of the radially outer open ends of recesses 37 exceeds that of recesses 38'.

While, in accordance with the patent statutes, we have disclosed specific details of a preferred embodiment of the invention, it is t9 be understood that these details are merely illustrative, and that many variations thereof may be made without departing from the spirit and scope of the invention. It is, therefore, our desire that the language of the accompanying claims be interpreted as broadly as possible, and that it be limited only by the prior state of the art.

We claim as our invention:

1. A selector switch for tap-changing regulating transformers including:

(a) a plurality of fixed contacts intended to be conductively connected to taps of a tapped transformer winding, said plurality of contacts being arranged in a common plane in a circular pattern, and some of said plurality of fixed circular contacts having an unequal circular pitch;

(b) a contact arm pivotable about an axis situated in the center of said circular pattern at right angles to said common planes and having a movable contact adjacent the radially outer end thereof for engaging each of said plurality of fixed contacts;

(0) a rotatable crankshaft for operating said contact arm, said crankshaft having rotatable pin means extending parallel to said axis in the center of said circular pattern; and

(d) a geneva gear driven by said crankshaft and driving said contact arm, said geneva gear having a plurality of recesses having open entrances engageable by said pin means, each of said plurality of recesses having a radially inner closed end portion of predetermined width and said predetermined width of said radially inner closed end portion of each of said plurality of recesses being equal, and said open entrances of each of said plurality of recesses having a predetermined width and said predetermined width of said open entrances of said plurality of recesses being unequal to convert equal angular motions of said pin means into motions of said contact arm corresponding to the unequal circular pitch of said plurality of fixed contacts.

2. A selector switch for tap-changing regulating transformers comprising in combination:

(a) a first plurality of fixed contacts intended to be conductively connected to the odd numbered taps of a tapped transformer winding, said first plurality of contacts being arranged in a circular pattern in a first common plane, and some of said first plurality of contacts having an unequal circular pitch;

(b) a second plurality of fixed contacts'intended to be connected to the even numbered taps of a tapped transformer winding, said second plurality of contact being arranged in a circular pattern in a second common plane parallel to said first plane, some of said second plurality of contacts having an unequal circular pitch, and the circular pattern formed by said second plurality of contacts being arranged in coaxial relation and angularly displaced relati've to the circular pattern formed by said first plurality of contacts;

(c) a first contact arm pivotable about the common axis of said circular pattern formed by said first plurality of contacts and said circular pattern formed by said second plurality of contacts and having a movable contact adjacent the radially outer end thereof for engaging each of said first plurality of contacts;

(d) a second contact arm pivotable about said common axis and having a second movable contact adj'acent the radially outer end thereof for engaging each of said second plurality of contacts;

(e) a rotatable crankshaft for jointly operating said first contact arm and said second contact arm, said crankshaft including a pair of pin means extending parallel to said common axis and angularly displaced degrees relative to each other;

(f) a first geneva gear driving said first contact arm and having a plurality of recesses with open entrances engageable by said first pin means, some of said plurality of recesses having geometrical configurations differing from the geometrical configuraof others of said plurality of recesses and the contours of said plurality of recesses being adapted to convert equal angular motions of said first pin means into motions of said first contact arm corresponding to the circular pitch of said first plurality of contacts; and

(g) a second geneva gear driving said second contact arm and having a plurality of recesses with open entrances engageable by said second pin means, some of said plurality of recesses having a geometrical configuration differing from the geometrical configuration of others of said plurality of recesses and the contours of said plurality of recesses being adapted to convert equal angular motions of said second pin means into motions of said second contact arm corresponding to the circular pitch of said second plurality of contacts.

3. A selector switch as specified in claim 1 wherein said plurality of recesses include recesses having a relatively widely radially outwardly flaring entrance portion and at least one recess having a relatively narrow entrance portion, said recesses having a relatively widely radially outwardly flaring entrance portion having a narrower circular spacing from each other than from said one recess having a relatively narrow entrance portion.

4. A selector switch as specified in claim 2 wherein said first geneva gear and said second geneva gear each have a plurality of recesses having relatively wide open entrance portions and a relatively small circular pitch, said first geneva gear and said second geneva gear forming a pair of geneva gears of which one geneva gear has but one recess having a relatively narrow entrance portion and a relatively large circular pitch, and of which the other geneva gear has two recesses having a relatively narrow open entrance portion and a relatively large circular pitch.

References Cited UNITED STATES PATENTS 3,250,864 5/1966 Bleibtreu et a1.

ROBERT K. SCHAEFER, Primary Examiner I. R. SCOTT, Assistant Examiner U.S. Cl. X.R. 

